FSavoy
commented
5 years ago Hi XiangMjjj,
Thanks a lot for your interest in our work. The question you are rising was in fact a key decision point in this sky imager project. Our first few sky imager prototypes used a sun blocker. We removed it in later prototypes.
There are three key considerations here:
- We realized that the sensor damage issue does not happen when we use a DSLR camera. In DSLR cameras, a mechanical shutter diverts the light to the viewfinder all the time except during actual image capture. This means that the sensor is only exposed to the sun light a fraction of the time. In contrast to this, the sun light is constantly hitting the sensor of mirror-less cameras, independently of whether an actual image is being captured. This is the scenario in which sensor damage can happen.
- The dynamic range of the image is much higher when there is no sun blocker. We mitigate this by capturing 3 images under different exposure settings. The brightest one captures most details around the sun while being undersaturated in other areas. The darkest one captures most details over the horizon while being oversaturated near the sun. A third image acts as a middle ground. We then compute a HDR image out of these 3 shots.
- We realized that the mechanical part of the shutter is the weakest point of our design. Due to the very high number of images being captured, the shutter would usually break after a few months. You might want to refer to a shutter lifetime database (such as https://shuttercheck.app/data/) to choose an appropriate camera and estimate the shutter repair cycle.
I hope this clarify your concerns. Please let me know if you have any other question.
Florian
On Mon, 21 Oct 2019 at 23:03, XiangMjjj notifications@github.com wrote:
I really appreciate your manual about DIY-Sky-Imager, it do help me to understand the necessary hardwares about imager system. However I have a question about camera protetion.For instance,TSI or WSC, their sky imager are equippped with the black band to prevent the sun directly shinning to CCD, but you just capture the sky directly(through a clear glass), making it possible that the CCD of the camera get damaged by sun. Is it a good way that the camera can normally operate for a long time(such as a year or several years)?In a word, I want to know is it possible to picture the sky photo where the sun is in the photo at the same time. Anyway, thanks for your introduction about diy-sky-imager.
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XiangMjjj
I really appreciate your manual about DIY-Sky-Imager, it do help me to understand the necessary hardwares about imager system. However I have a question about camera protetion.For instance,TSI or WSC, their sky imager are equippped with the black band to prevent the sun directly shinning to CCD, but you just capture the sky directly(through a clear glass), making it possible that the CCD of the camera get damaged by sun. Is it a good way that the camera can normally operate for a long time(such as a year or several years)?In a word, I want to know is it possible to picture the sky photo where the sun is in the photo at the same time. Anyway, thanks for your introduction about diy-sky-imager.